In Pennsylvania thousands of wells have been put into production over the past four years, but about 2,000 more have been drilled but not completed, leaving plugged holes in the ground. The backlog means it is far cheaper for a company to bring those wells into production than to start others from scratch in neighboring states.

A new report from Bentek Energy, which examines national industry trends, estimates that even if companies stopped drilling new wells in northeast Pennsylvania, production could grow by 31 percent over the next 16 months as the partly drilled wells get hooked up.

Bentek also found that in April, Pennsylvania's Marcellus production hit about 5.3 billion cubic feet of gas per day, with another 1.5 billion coming from West Virginia. That's about seven times the rate of just three years ago, and the boom has led to a steep drop in wholesale natural gas prices.